P and converted S waves observed in refraction stations FF1, FF2, and FF4 of the 1959 Fanfare cruise of the Scripps Institution of Oceanography are analyzed by synthetic seismogram modeling of the data using the reflectivity algorithm and by inversion of the P and S wave travel time data to obtain extremal bounds on the P and S velocity (vp and vs profiles. While the FF1 data are inadequate for detailed an alysis, the FF2 and FF4 data yield vp profiles displaying rapidly increasing velocity with depth in layer 2, a small velocity discontinuity between layers 2 and 3, gently increasing velocity with depth in layer 3, and a 1-km-thick Moho transition. The vs profiles for FF2 and FF4 show rapidly increasing velocity with depth in layer 2, fairly uniform velocities in the top of layer 3, a slight low-velocity zone extending through most of layer 3, and a 1-km-thick Moho transition. Using theories of seismic wave velocities in cracked media and a laboratory velocity measurement made on a basalt sample from this site, a porosity of 18% is inferred for the top of the igneous crust at this site. A further reduction of porisity of 2% can explain the observed velocity gradients only to a depth of 0.6 km into the igneous crust. In the 0.8- to 1.5-km depth interval, Poisson's ratio appears to drop below 0.27 to a minimum of 0.24, which may indicate a zone of trondhjemites or other quartz-rich rocks at this depth or which may be related to state of fluid saturation of the rocks. Within layer 3, observed vp and vs agree well with laboratory velocity measurements of ophiolite samples from western U.S. and from the Bay of Islands, Newfoundland. The observed velocities suggest the disappearance of horn-blende and the appearance of augite and olivine with increasing depth in layer 3. There is no evidence for more than 30% serpentine anywhere within the crust or upper mantle at this site, except possibly within unresolvably thin zones or pods. Evidence is also given which suggests that velocities and velocity gradients in the shallow crust may be partly controlled by differential pressure (externally applied pressure minus pore fluid pressure) and its spatial gradients and that laboratory velocity measurements made on water-saturated basalt samples at zero differential pressure are more representative of in situ velocities in the shallow crust than lab measurements made at which are usually employed as in situ conditions, namely, elevated externally applied pressure and zero pore fluid pressure. The factors affecting the efficiency of shear wave conservation at the sea floor are investigated, and the important role of basement vp and espatially vs are shown. Since basement vs is very sensitive fracture geometry, the high lateral variability of shear wave conversion may be related to variability in the extent and character of basement porosity. A useful explosive source function for marine synthetic modeling is presented, and nomenclature for marine seismic phases is suggested.